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Safety and Paint
A new Singapore Standard provides the specifications of
a ready-to-use paint suitable for use as a primer in the protection of
iron and steel surfaces for both indoor and outdoor use. SS 494:2001 Specification
for lead and chromate-free primer for iron and steel substrate has been
developed specifically to address the toxicity and other environment and
health effects of red lead and zinc chromate.
Harmful effects of red lead and zinc chromate
Currently, there are two Singapore Standards for metal primers. They
are :
1) SS 6 : 1995 "Specification for red lead based primer
for iron & steel surfaces"
2) SS 206 : 1981 "Specification for zinc chromate primer"
In Singapore, these paints are used by the construction industry and for
steel structures used in civil and marine engineering. However, red lead
and zinc chromate are highly toxic metals that can produce a range of
adverse health effects.. Lead compounds are bio-accumulative and ingestion,
inhalation or skin absorption of red lead can lead to skin disorders,
neuro-muscular dysfunction, possible paralysis and even death. Likewise,
hexavalent chrome in zinc chromate pigments is a known carcinogen and
is likely to cause dermatitis, skin sensitisation and reproductive disorders.
Awareness of the toxicity of these compounds have been gaining momentum
since the late 1970s and this has led to gradual control and legislation
in the use of these pigments.
The move to ban the use of lead and hexavalent chromate based pigments
in paints in developed countries, notably in the US, has triggered active
research in the development of new environmentally friendly and non-toxic
anti-corrosive pigments. Many new pigments have since been introduced.
Substitutes such as zinc phosphate, calcium phosphate, aluminium phosphate,
barium metaborate, phos-phosilicates, borosilicates as well as some proprietary
compositions have been widely studied to determine their performance as
primers versus that of the red lead and zinc chromate primers.
Towards a safer product
A sector-wide project was started in 1997 by PSB and nine
Singapore Paint Manufacturers' Association (SPMA) members with funding
from EDB's Innovation Development Scheme (IDS). The aim was to formulate
a lead and chromate-free primer with comparable performance to the reference
red lead and zinc chromate primers. The jointly developed prototype has
shown promising results with almost equivalent characteristics to the
original lead and zinc primers when tested under salt spray and prohesion
test conditions. The duration of these tests on these prototypes is much
longer than the current requirements in both SS 6 : 1995 and SS 206 :
1981 coatings standards. With the prototype formulation, participating
members fine-tuned their own formulations.
A Working Group (WG) was appointed in August 1999 to undertake the final
work relating to the development of lead and chromate-free primer for
steel substrate and establishment of a Singapore Standard. During the
WG deliberations, there was close collaboration on technology between
the Singapore Paint Manufacturers which resulted in the successful development
of an environmentally friendly primer that is effective in inhibiting
corrosion of steel substrates under tropical climatic conditions.
Participating members of the project were invited to manufacture production
batches based on their own modified or fine-tuned formulations and the
properties of each individual company's product were then tested. The
most important criteria was the performance of the product in relation
to corrosion.
This Singapore Standard will serve as a performance standard for specifiers
like the architect to protect iron and steel substrates from corrosion
using environmentally safe products.
By Dr Lim Chooi Seng, PSB Corporation
Pte Ltd and Convenor of WG for Lead and Chromate-Free Primer for Steel
Substrates.
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